1. Technical Field
This invention is an oil well equipment apparatus, and more particularly, an apparatus for mixing and injecting into a well tubular a dry material/liquid slurry.
2. Description of Related Art
It is often necessary to perform operations on producing oil wells to restore or increase production. These operations are typically called "work overs." Some work overs involve temporarily "plugging back" a lower subterranean formation or strata with sand or other materials so that operations may be performed on an upper subterranean formation or strata to restore and/or increase the production thereof. Pursuant to this procedure, the lower subterranean formation or strata is covered so that treating fluids can be pumped via a well into the upper subterranean formation or strata without entering the covered lower formation or strata. To effect the plugging back of the lower formation or strata, a dry particular material, such as sand, is mixed with a liquid, such as water, to form a particulate/liquid slurry which is injected into a well penetrating both the upper and lower formation or strata. The sand is deposited in the well and plugs the lower formation or strata thereby allowing work over in the upper formation or strata. Plugging back with sand requires that a uniform continuous slurry of sand and water be injected into the well. Commonly, sand is slowly dumped from a sack into well tubing while being washed down the tubing with water from a hand held hose. Although simple to perform, this method is slow and does not provide a sand/water slurry with a uniform composition. Alternatively, a premixed slurry of sand and gelled water ha been pumped into the well tubing. This method provides a consistent and uniform sand/water slurry, but requires a gel which is an added expense and is time consuming to prepare. Further, this method requires special equipment and labor to mix and pump the slurry which adds expense to the method.
Early attempts to develop mixture apparatus are exemplified by U.S. Pat. No. 4,444,277 to Lewis which discloses an apparatus and an associated method for conditioning or reconditioning oil well drilling mud, comprising multiple hoppers for holding dry additive. Each hopper has a mechanism permitting the additive to be fed into an entrainment chamber at pre-selected rates. An auger is used to force the dry additive through an adjustable gate valve to control the additive flow rate into the entrainment chamber. The additives are mixed at controlled rates with a free jet of mud forced perpendicularly across the entrainment chamber. The mud with entrained additives is collected in a reservoir from which it is forced by a high pressure well pump into a drill stem.
U.S. Pat. No. 4,944,347 to Richard and Johnson discloses an apparatus for providing a direct high velocity, consistent, uniform preparation of completion/workover systems for use in a subterranean well. The apparatus has a screw type conveyor extending through a mixing housing which is in direct communication with a pump. Passageways are provided through the housing for a screw type rotatable conveyor and through a mixing chamber housing in axial alignment with openings in a pump such hat the diametric area between the interior of the housing and the exterior of the conveyor housing provides sufficient transport velocity for the carrier fluid and the solid particular matter from the point of mixing in the annulus, through the annulus and to the inlet of the pump. A pump injects the carrier fluid/particular matter mixture into a fluid transmission conduit and therefrom into a well.
U.S. Pat. No. 2,005,800 to Boyle discloses a mixing apparatus for mixing well drilling fluids. The apparatus comprises a tubular container having a hopper arranged to deliver material into the container. A water line enters the container and terminates in the container at a jet nozzle located underneath and adjacent the hopper. The water line has a valve accessible from the outside of the container and arranged to regulate water flow through the water line and into the jet nozzle. A mixing device is also incorporated into the container downstream of the hopper. The jet nozzle is aligned perpendicular to the fixably attached hopper to entrain material from the hopper in a water jet for the jet nozzle. The water with entrained matter passes through the mixing device and is stored in a vat prior to use.
U.S. Pat. No. 2,372,957 to Keefer discloses an apparatus for storing and feeding an abrasive such as sand to a hydraulic blast gun wherein the sand particles are moved forward by means of a high velocity jet of liquid. The apparatus consists of a hopper or bin adapted to receive and store a quantity of abrasive material. A jet is arranged beneath the hopper to develop a partial vacuum to draw or suck abrasive material into the gun and entrain the material into a liquid stream. The jet is positioned perpendicular to the flow of abrasive from the hopper. The water/abrasive mixture is then used in a hydraulic blast gun for sand blasting type operations.
All of the above cited apparatuses provide dry material/liquid mixing yet are not portable and are not attached directly to a well penetrating a subterranean formation or strata so as to inject uniform material/liquid slurries in to the well. Accordingly, each of the above cited apparatuses require special equipment including pumps to transfer slurries to the wellhead for injection into the well. The above cited apparatuses also do not have hoppers which are detachable from the mixing apparatus to facilitate easy cleaning and maintenance nor do the apparatuses have means for supporting containerized material near the inlet of their hoppers to aid manual pouring of dry material such as bagged sand or cement into the hoppers. Finally, the above cited apparatuses all utilize gravity fed material entrainment by liquid jets from horizontally positioned jet nozzles. This results in an inefficient translation of energy from a vertical to a horizontal plane which is an inefficient use of available gravity and jet energy for mixing. Thus, a need therefore exists for an apparatus which will mix a dry material with a liquid to provide a consistent, uniform material/liquid slurry which can be injected directly into a well yet does not require premixing with a gel. Ideally, this apparatus would be portable, have means for supporting containerized dry material such as shelving to assist manual pouring of bagged materials into the apparatus, have a detachable hopper to facilitate maintenance and cleaning of the apparatus and can be easily attached to and released from the well which is to be worked over. The apparatus would also utilize gravity feeding of dry material and entrainment of the dry material by a vertically directed jet of liquid.
Accordingly, it is an object of the present invention to provide an apparatus for mixing and injecting a dry material/liquid slurry into a well, which is portable, is easily attached to and removed from a well tubular, is comprised of a detachable hopper with means for supporting containerized dry material to assist manual pouring of dry material into the apparatus, and utilizes gravity feeding of dry material from a hopper to a vertically directed liquid jet.
It is a further object of the present invention to provide an apparatus for mixing and injecting a dry material/liquid slurry into a well, which mixes and injects such a slurry at a faster rate than convention apparatuses.
It is a still further object of the present invention to provide such a mixing apparatus which does not require special pumping equipment to transfer the dry material/liquid slurry to the wellhead for injection.